1. Field of the Invention
The present invention relates to a comb structure using a magnetic force, an actuator and an inertia sensor which use the comb structure, and more particularly, to a comb structure in which a magnetic force, which is generated between a pair of interlocked combs by applying a magnetic flux thereto, is constant with respect to the relative motion between the combs, and to an actuator and an inertia sensor both using the comb structure.
2. Description of the Related Art
In many cases, electrostatic actuators and magnetic actuators are used to move micro structures. An electrostatic comb drive (U.S. Pat. No. 5,025,346) is well known as an electrostatic actuator. The basic principle of the electrostatic comb drive will now be described with reference to FIG. 1.
A pair of combs 1 and 2 mesh with each other with a gap S between fingers thereof. When a power supply voltage 3 is connected to each of the combs 1 and 2 via conductive wires 4 and 5, respectively, a horizontal electrostatic force 6 acting upon a finger of the comb 2 is expressed by the following Equation 1:                               F          S                =                              ϵ            0                    ⁢                      t            s                    ⁢                      xe2x80x83                    ⁢                      V            2                                              (        1        )            
wherein xcex50, t, s and V denote the permittivity of free space, the thickness of a finger, the interval between the finger of the comb 2 and an adjacent finger of the comb 1, and a voltage 3 applied to a bridge between fingers, respectively. The electrostatic comb driver can be manufactured by a CMOS process such as a process for manufacturing a semiconductor RAM, and has a constant force with respect to the motion of a comb as shown in Equation 1. However, the force is too weak to directly drive large structures.
As an example of a magnetic actuator, an actuator is introduced by E. Fullin et al. [xe2x80x9cA New Basic Technology for Magnetic Micro Actuatorsxe2x80x9d, Proceedings of IEEE Micro Electro Mechanical Systems, pp 143-147, 1998]. The magnetic actuator is conceptually shown in FIG. 2. In this magnetic actuator, a pair of magnetic plates 11 and 12 face each other having an interval h therebetween, and each is connected to a magnetic flux guide 13. A coil 14 is wound around a portion of the magnetic flux guide 13. The coil 14 is connected to the power supply voltage 15, such that it generates an electromotive force when a current flows through the coil 14, thereby forming a magnetic circuit which connects to the magnetic flux guide, the two plates 11 and 12 and the gap h. In this case, most of the magnetic resistance in the circuit is in the gap h, so that a magnetic force 16 acting upon the plate 12 can be expressed by the following Equation 2:                               F          s                =                                            μ              0                        2                    ⁢                      A                          h              2                                ⁢                                    (              NI              )                        2                                              (        2        )            
wherein xcexc0, A, h and NI denote the permeability of free space, the area of each of the plates 11 and 12, the interval between the plates 11 and 12, and an electromotive force depending on the number of windings of the coil 4 and the flow of current, respectively. Referring to Equation 2, the magnetic force in an existing structure is inversely proportional to the square of the interval between the two plates, h. Thus, there are problems in that it is difficult to control the position of the existing structure, and the upper plate becomes attached to the lower plate.
To solve the above problems, an objective of the present invention is to provide a comb structure using a magnetic force, by which a strong force can be provided to drive a large structure, and the position of a structure can be easily controlled, and an actuator and an inertia sensor both using the comb structure.
Accordingly, to achieve the above objective, there is provided a comb structure using a magnetic force, including a board, a suspension structure, at least one supporter, at least one elastic member, a movable comb, a fixed comb, and at least one magnetic flux guide. The suspension structure, which is an inertia body, is separated a predetermined height from the board while maintaining the predetermined height from the board. The at least one supporter supports the suspension structure so that the suspension structure is spaced from the upper surface of the board. The at least one elastic member connects the suspension structure to the supporter and supporting them so that the suspension structure makes an inertial movement over the substrate. The movable comb has at least one finger, is attached to the suspension structure, and maintains a predetermined interval from the substrate. The fixed comb is fixed onto the board such that the fixed comb is opposite to the movable comb, intermeshing with the movable comb. The at least one magnetic flux guide induces a magnetic flux between the fixed comb and the suspension structure. A magnetic circuit comprised of a combination of the fixed comb, the suspension structure and the magnetic flux guide, is formed. When a magnetomotive force is applied to the magnetic circuit, a magnetic flux flows between the movable comb and the fixed comb to generate a magnetic force, and the suspension structure is formed so that it is excited.
In the present invention, a coil is wound around a portion of the magnetic circuit, and a power supply is supplied to the coil, thus generating the magnetomotive force. Alternatively, a magnet is installed on a portion of the magnetic circuit, thus generating the magnetomotive force. Preferably, the magnetic flux guide is connected to the supporter and a supporting unit for the fixed comb to form a magnetic flux guide on the movable comb and the fixed comb. Also, it is preferable that a moving unit comprised of the suspension structure, the movable comb and the elastic member is formed to install a magnetic flux guide on the movable comb and the fixed comb, and that the magnetic flux guide extends from a location that is separated from the moving unit by a predetermined distance, to the supporting unit for the fixed comb.
Also, preferably, in the suspension structure, the movable comb and the supporter are incorporated in a body such that the incorporated body moves horizontally with respect to the board, or the movable comb and the supporter are incorporated in a body such that the incorporated body rotates with respect to the support. It is preferable that a moving unit comprised of the suspension structure, the movable comb and the elastic member is formed to install a magnetic flux guide on the movable comb and the fixed comb, and that the magnetic flux guide is driven by the resonance frequency of the moving unit.
To achieve the above objective of the present invention, there is provided an actuator including a board, a suspension structure, at least one elastic member, a movable comb, a fixed comb, at least one magnetic flux guide, a coil, and a power supply. The suspension structure, which is an inertia body, is separated a predetermined height from the board, maintaining the predetermined interval with the board. The at least one supporter supports the suspension structure so that the suspension structure is spaced from the upper surface of the board. The at least one elastic member connects the suspension structure to the supporter and supporting them so that the suspension structure makes an inertial movement over the substrate. The movable comb has at least one finger, is attached to the suspension structure, and keeps a predetermined interval from the substrate. The fixed comb is fixed onto the board so that a predetermined interval is maintained between the fixed comb and the movable comb, the fixed comb being meshed with the movable comb opposite thereto. The at least one magnetic flux guide flows a magnetic flux between the fixed comb and the suspension structure. The coil winds around a predetermined portion of the magnetic flux guide. The power supply flows a current in the coil to generate a magnetomotive force. A magnetic circuit comprised of a combination of the fixed comb, the suspension structure and the magnetic flux guide, is formed. When a magnetomotive force generated by flowing a current in the coil is applied to the magnetic circuit, a magnetic flux flows between the movable comb and the fixed comb to generate a magnetic force, and the suspension structure is formed so that it is excited.
To achieve the above objective of the present invention, there is provided an inertial sensor using a comb structure using a magnetic force, the inertial sensor including a board, a suspension structure, at least one support, at least one elastic member, a movable comb, a fixed comb, at least one magnetic flux guide, and a magnetomotive force. The suspension structure, which is an inertia body, is separated a predetermined height from the board, maintaining the predetermined interval with the board. The at least one supporter supports the suspension structure so that the suspension structure is spaced upward from the board. The at least one elastic member connects the suspension structure to the supporter and supporting them so that the suspension structure makes an inertial movement over the substrate. The movable comb has at least one finger, is attached to the suspension structure, and keeps a predetermined interval from the substrate. The fixed comb is fixed onto the board so that a predetermined interval is maintained between the fixed comb and the movable comb, the fixed comb being meshed with the movable comb opposite thereto. The at least one magnetic flux guide induces a magnetic flux between the fixed comb and the suspension structure. The magnetomotive force generator induces a current in the magnetic flux guide. A magnetic circuit comprised of a combination of the fixed comb, the suspension structure and the magnetic flux guide is formed, and a variation in inertia depending on the motion of the suspension structure (i.e, a variation in distance between the fixed comb and the movable comb) can be detected by comprising a magnetic flux sensor for sensing a magnetic flux which flows in the magnetic flux guide.
In the present invention, the magnetomotive generator includes a coil wound around a predetermined portion of the magnetic flux guide; and a power supply for inducing a current in the coil to generate a magnetomotive force. Alternatively, the magnetomotive generator is a permanent magnet installed on a predetermined portion of the magnetic flux guide. Preferably, the magnetic flux sensor is a coil wound around a predetermined portion of the magnetic circuit.